Electrical connector with frequency-tuned groundplane

ABSTRACT

An electrical connector with a frequency-tuned groundplane is disclosed. The connector includes a signal medium to communicate an electrical signal and a frequency-tuned groundplane medium to communicate a reference voltage (i.e., ground). The groundplane medium differentially supplies the reference voltage to the groundplane second end, responsive to the frequency of the electrical signal. In one aspect, the first groundplane layer conductive trace includes a transmission line pattern, and the second groundplane layer conductive trace is connected to the first groundplane layer conductive trace through a plurality of conductive vias. For example, the first groundplane layer may include a plurality of conductive patches, some of which have a via connection to the second groundplane layer conductive trace.

FIELD OF THE INVENTION

This invention generally relates to wireless communications and, moreparticularly, to a connector that is frequency-tuned to minimize theconduction of ground currents at particular selected radiationfrequencies.

BACKGROUND OF THE INVENTION

Consumers are demanding smaller and feature-rich wireless communicationdevices, such as cellular (cell) telephones. A smaller cell phone withmore functions and features can be produced with two housing portions.One such configuration is a flip phone. A flip phone opens up like aclamshell. Other configurations are sliding phones and swivel phones. Ina sliding phone, one portion of the cell phone housing slides relativeto the other portion. In a swivel phone, one portion of the cell phoneswivels open, relative to the other portion. A sliding phone is shown inSer. No. 10/931,712, filed on Sep. 1, 2004, by the instant assignees,the disclosure of which is hereby incorporated herein by reference inentirety.

Typically, one arrangement of the two housing portions is smaller thanthe other. The smaller arrangement is often called the closedconfiguration, and the larger arrangement is called the openconfiguration. The cell phone user can keep the cell phone in the closedconfiguration when carrying the cell phone, or for storage. In use, thecell phone is put in the open configuration. Some phones can be used inboth configurations.

In some configurable cell phones, both housing portions have a groundplane. Ground planes often act as the counterpoise for proximateantennas and almost always affect antenna performance. An antenna mightperform optimally with the cell phone in one (i.e., open) configuration,but sub-optimally with the cell phone in the other (i.e., closed)configuration. The sub-optimal performance may be due to the positionalchange of one of the ground planes relative to the antenna. An antennathat depends heavily on the ground plane, such as a patch antenna,planar inverted-F antenna (PIFA), or folded monopole, may perform poorlywhen a grounded metal is near the antenna in some configurations.

Poor antenna performance can be characterized by the amount of currentunintentionally generated through a transceiving device, typically assurface currents, as opposed to amount of energy radiated into theintended transmission medium (i.e., air). From the point of view of atransmitter, poor antenna performance can be measured as less radiatedpower, or less power in an intended direction. From the receiverperspective, poor antenna performance is associated with degradedsensitivity due to noisy grounds. From either point of view, poorperformance can be associated with radio frequency (RF) ground currents.

The above-mentioned ground issues are compounded with the use oftwo-part clamshell type cell phones. Many cell phones use so-called flexfilms to carry signals between the two phone halves, for example,between a liquid crystal display (LCD) module and the main printedcircuit board (PCB). These flex films are conventionally multi-layeredplanes of grounds and signal lines formed on, and separated by flexiblesheets of dielectric insulator materials. These long thin signal wiresmay unintentionally act as antennas, interfering with the intendedantennas and degrading the receiver performance. At the cost ofconnector flexibility, silver ink shielding (ground) layers can be usedto cover the connector, or even added as internal layers. While thisbrute-force approach does shield the connector signal lines, otherproblems may be introduced. Since the shielded connector is locatedproximate to the antenna, the intended radiation patterns can bealtered. Using a cell phone as an example, the shielded flex connectormay cause a desired upward-pointing radiation pattern in the PCS band topoint in an alternate, less desirable direction.

SUMMARY OF THE INVENTION

The device described herein is a flexible connector with a groundplanethat prevents current flow at particular radiation frequencies, betweenhalves of a two-part wireless communications device. By controllingcurrent flow between the device halves at the radiation frequencies, theground geometry of the antenna can be made dependent upon thegroundplane effects of the connected device half, or not. For example,at one frequency the connector may choke ground current flow between thedevice halves, while freely conducting ground current flow at a secondfrequency. As a result, antenna performance is optimized and receiverdegradation is minimized.

Accordingly, an electrical connector is provided with a frequency-tunedgroundplane. The connector comprises a signal medium having a firstsignal end to accept an electrical signal and a second signal end tosupply the electrical signal, and a frequency-tuned groundplane medium.The groundplane medium is adjacent the signal medium and has a firstgroundplane end to accept a reference voltage, defined with respect tothe electrical signal, and a second groundplane end to supply thereference voltage. For example, the reference voltage can be a ground.The groundplane medium differentially supplies the reference voltage tothe groundplane second end, responsive to the frequency of theelectrical signal.

Typically, the signal medium includes at least one signal layer of aflexible dielectric material with a conductive trace. Then, thegroundplane medium includes a first layer of flexible dielectricmaterial with a conductive trace overlying the signal layer, and asecond layer of flexible dielectric material with a conductive trace, inelectrical communication with the first groundplane layer conductivetrace, underlying the signal layer.

More specifically, the first groundplane layer conductive trace maycomprise a transmission line pattern, and the second groundplane layerconductive trace may be connected to the first groundplane layerconductive trace through a plurality of conductive vias. For example,the first groundplane layer may include a plurality of conductivepatches, some of which have a via connection to the second groundplanelayer conductive trace.

In one aspect, the second groundplane layer conductive trace comprises atransmission line pattern. Alternately, the second groundplane layer isa substantially uniform conductive trace. In another variation, thetransmission line characteristics of the ground alternate between thefirst and second groundplane layers. For example, in one portion of theconnector a second groundplane layer conductive trace, formed as atransmission line, may overlie a substantially uniform (frequencyinsensitive) region of first groundplane layer conductive trace. Then,in an adjacent portion of the connector the first groundplane layerconductive trace, formed as a transmission line, may overlie asubstantially uniform region of second groundplane layer conductivetrace. In this manner, the transmission line pattern alternates betweengroundplane layers.

Additional details of the above-described connector, and a method forconducting ground current in an electrical connector, responsive tofrequency, are provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing of an electrical connector with afrequency-tuned groundplane.

FIG. 2A is a partial cross-sectional view of an electrical connectorwith a frequency-tuned groundplane.

FIGS. 2B, 2C, and 2D are plan views of the groundplane first layer,signal layer, and groundplane second layer, respectively.

FIGS. 2E and 2F are plan views of first and second alternate aspects ofthe groundplane first layer.

FIG. 3 is a plan view of a third variation of the first groundplanelayer trace.

FIG. 4 is a plan view of a fourth variation of the first groundplanelayer trace.

FIG. 5 is a perspective view of a fifth variation of the firstgroundplane layer trace, with a transmission line pattern secondgroundplane layer trace.

FIG. 6 is a schematic block diagram of a segmented wirelesscommunications device with a frequency-tuned connector groundplane.

FIG. 7 is a flowchart illustrating a method for conducting groundcurrent in an electrical connector, responsive to frequency.

FIG. 8 is a schematic diagram depicting the first groundplane conductivetrace of FIG. 3.

DETAILED DESCRIPTION

FIG. 1 is a schematic drawing of an electrical connector with afrequency-tuned groundplane. The connector 100 comprises a signal medium102 having a first signal end 104 to accept an electrical signal and asecond signal end 106 to supply the electrical signal. A groundplanemedium 108 with a transmission line pattern is adjacent the signalmedium 102. The groundplane medium 108 has a first groundplane end 110to accept a reference voltage, defined with respect to the electricalsignal on line 102, and a second groundplane end 112 to supply thereference voltage. The reference voltage can be signal ground, chassisground, a dc voltage, or an ac ground, for example. The transmissionline pattern is represented, in its simplest form, as series-connectedinductive elements 114 that are shunted to ground through capacitors116. The groundplane medium 108 may be understood to be a transmissionline that differentially supplies the reference voltage to the secondend 112, responsive to the frequency of the electrical signal.Alternately stated, the inductive elements 114 and capacitive elements116 can be tuned to a maximum series impedance (or minimum shuntimpedance) at an intended frequency. Other, more complex, transmissionline schematic representations (not shown) are also suitable for usewith the present invention. The frequency-tuned groundplane can beenabled using a more complex type of transmission line.

FIG. 2A is a partial cross-sectional view of an electrical connectorwith a frequency-tuned groundplane. As in the schematic of FIG. 1, theconnector 100 comprises a signal medium 102 and a frequency-tunedgroundplane medium 108. For clarity, each layer is separated fromadjoining layers by a space that would not exist in a completelyassembled connector. In its simplest form, the signal medium 102includes a single signal layer 200 of a flexible dielectric materialwith a conductive trace 204. The flexible dielectric material may be amaterial such as an insulating film or paper. For example, the materialcan be a polyester or polyimide film, such as Mylar® or Kapton®. Othermaterial choices include a synthetic aromatic polyamide polymer, such asNomex®. Further, phenolic sheets or polytetrafluoroethylene (PTFE), suchas Teflon®, may be used. Chlorosulfonated polyethylene (i.e., Hypalon®),silicon sheets, ethylene propylene diene monomer (EPDM) are also goodmaterial choices. However, the dielectric is not limited to anyparticular material. A number of other conventional materials could beused to enable the invention. The conductive trace may be a materialsuch as copper, silver, conductive ink, tin, or any conventional printedcircuit conductor. However, the connector 100 is not limited to anyparticular materials. The groundplane layers are made from similarflexible materials and conductors.

The groundplane medium 108 includes a first groundplane layer offlexible dielectric material 206 with a conductive trace 208, overlyingthe signal layer 102. A second groundplane layer of flexible dielectricmaterial 210 with a conductive trace 212, is in electrical communicationwith the first groundplane layer conductive trace 208. The groundplanesecond layer 210 underlies the signal layer 200. As described below, theelectrical communication between groundplane layers can be accomplishedusing interlevel via connections or rivets. In other aspects of theconnector, the connection between layers can be accomplished usingstrips or ribbons of conductive materials wrapped around the edges(sides) of the connector.

FIGS. 2B, 2C, and 2D are plan views of the groundplane first layer,signal layer, and groundplane second layer, respectively. Although onlya single conductive trace 204 is shown in FIG. 2B, the connector is notlimited to any particular number of signal traces per layer. In otheraspects not shown, a plurality of signals layers, each with at least onesignal trace, may be formed between the first and second groundplanelayers. In the case of multiple signal layers, auxiliary groundplanelayers may be formed between signal layers.

In one aspect, the first groundplane layer conductive trace 208comprises a transmission line pattern, and the second groundplane layerconductive trace 212 is connected to the first groundplane layerconductive trace through a plurality of conductive vias 214. In someaspects, the size, placement, and spacing between vias 214 is part ofthe transmission line pattern. As shown, the first groundplane layerconductive trace 208 may include a plurality of conductive patches 216,each having a via connection 214 to the second groundplane layerconductive trace 212, which is depicted in cross-hatch as asubstantially uniform layer of conductive material. That is, the secondgroundplane layer trace 212 is not intended to be a transmission line orto have a frequency-responsive impedance. However, the connector is notnecessarily limited to such a second groundplane trace. In otheraspects, the second groundplane layer trace may also be formed as atransmission line, either independent or in cooperation with the firstgroundplane layer trace 208.

Each patch 216 has an inductance associated with its length 218. Thegroundplane layer conductive trace 208 then comprises the plurality ofpatches 216, placed consecutively lengthwise, capacitively coupled by afirst spacing 220. Although the first spacing 220 is shown as having astepped pattern shape, or patterns are also useful.

FIGS. 2E and 2F are plan views of first and second alternate aspects ofthe groundplane first layer. Straight line (FIG. 2E) and saw-toothedpatterns (FIG. 2F) are shown. The connector is not limited to anyparticular spacing pattern, or combination of spacing patterns.

Although each signal and groundplane layer has been shown as beingcomprised of an independent dielectric insulator with an overlyingconductive trace, the trace is not limited to placement on anyparticular surface of the insulator. In other aspects not shown,conductive traces can be formed on opposite sides of a common insulatorlayer. In a different aspect, conductive trace can be formed underlyinginsulator layers to preserve electrical integrity.

FIG. 3 is a plan view of a third variation of the first groundplanelayer trace. Patches 300 are connected to the second groundplane layertrace (not shown) through a via 214. Although only a single via is shownfor each patch 300, in other aspects not shown, each patch may beconnected with multiple vias. In some aspects, the size, placement, andspacing between vias 214 are part of the transmission line pattern.Patches 302 are capacitively coupled to the second groundplane layerconductive trace through one (or more) of the patches 300. That is,patches 302 are capacitively coupled to patches 300.

Each patch 300 has a width 304 and a length 306. Each patch 302 has alength 310, and an inductance associated with its width 308. The firstgroundplane layer 206 has a first edge 312 and a second edge 314.Patches 300 are placed consecutively lengthwise along each edge 312/314of the layer 206, capacitively coupled by a third spacing 316. Patches302 are placed consecutively lengthwise, capacitively coupling theinductance of each patch 302 with a fourth spacing 318. Patches 302 areseparated widthwise from the patches 300 at each edge 312/314,capacitively coupled by a fifth spacing 320. The second groundplanelayer trace (not shown) may be formed into a transmission line pattern,or as a substantially uniform (frequency-insensitive) layer of conductor(see FIG. 2D).

FIG. 4 is a plan view of a fourth variation of the first groundplanelayer trace. The first groundplane layer conductive trace 208 includes aplurality of patches 400. Each patch 400 has a width 402 and a viaconnection 214 to the second groundplane conductive trace (not shown).As depicted, each patch 400 is connected to the second groundplane layertrace with a plurality of vias 214 separated at regular intervals. Insome aspects, the size, placement, and spacing between vias 214 are partof the transmission line pattern. The patches 400 are placedconsecutively widthwise, capacitively coupled by a second spacing 403.Although only three patches are shown in this variation, the inventionis not limited to any particular number of lengthwise patches 400.

FIG. 5 is a perspective view of a fifth variation of the firstgroundplane layer trace, with a transmission line pattern secondgroundplane layer trace. Note, for clarity, the intervening signalmedium layer is not shown. Here, the transmission line patternalternates between the first and second groundplane layer traces. In afirst section 500, a transmission line pattern second groundplane layerconductive trace 212 underlies a substantially uniform (non-frequencydependent) region of first groundplane layer conductive trace 208 shownin cross-hatch. In a second region 502, a transmission line patternfirst groundplane layer conductive trace 208 overlies a substantiallyuniform region of second groundplane layer conductive trace 212 shown incross-hatch. In other aspects not shown, both the first and secondgroundplane layer conductive traces may be formed as transmission lines,or there may be an overlap in transmission line patterns between layers(regions 500 and 502 overlap). As above, the two groundplane layers areconnected with vias 214 (for clarity only two vias are shown).

FIG. 6 is a schematic block diagram of a segmented wirelesscommunications device with a frequency-tuned connector groundplane. Aflip or clamshell phone is an example of a segmented device. The device600 comprises a first device segment 602 with electrical circuitry, anda second device segment 604 with electrical circuitry. An electricalconnector 100 has a first connector end 608 connected to the firstdevice segment 602, and a second connector end 610 connected to thesecond device segment 604. As generally described in FIGS. 2A through 5,the electrical connector 100 comprises a signal layer of flexibledielectric material with a conductive signal trace, a first groundplanelayer, and a second groundplane layer. The first groundplane layerincludes a flexible dielectric material with a conductive trace, formedin a transmission line pattern, overlying the signal layer. The secondgroundplane layer includes a flexible dielectric material with aconductive trace, in electrical communication with the first groundplanelayer conductive trace, underlying the signal layer. Details of theconnector have been presented above, and will not be repeated in theinterest of brevity.

In one aspect, the first device segment 602 includes an antenna 612operating at a first frequency. The connector 100 minimally conductsground current at the first frequency.

For the purposes of illustration it has generally been assumed that theabove-described antennas have been designed to operate with only onedevice half. For example, with respect to FIG. 6 it has been assumedthat the antenna 612 preferably operates at the first frequency inassociation with the groundplane of the first segment 602, but not thesecond segment 604. However, at a second frequency the antenna maypreferably operate in association of groundplanes of both the first andsecond device segments. In this case the flex connector 100 would bedesigned to conduct second frequency ground current between the firstsegment 602 and the second segment 604.

Alternately, the first segment 602 may have a second antenna (notshown), which is designed to operate in association with thegroundplanes of both the first and second segments. In thiscircumstance, the connector may act to minimize ground currentsresponsive to the first antenna, while maximizing ground current flowresponsive to the second antenna.

In another variation not shown, each device segment may have an antenna.Assuming that the two antennas are not operating at the same frequency,the connector may be tuned to minimize ground current flow responsive tothe antenna 612 on first segment 602, while maximizing ground currentflow associated with the second antenna on the second segment.

Alternately considered, FIG. 6 may represent a communications device 600with a frequency-selectable antenna counterpoise. The device 600comprises an antenna 612, and a first counterpoise 602 to supply aconstant (frequency-insensitive) antenna ground. For example, theantenna can be a style that is sensitive to groundplane placement, suchas a PIFA, monopole, or patch antenna. An electrical connector 100 has afirst connector end 608 connected to the first counterpoise 602, and asecond connector end 610. As explained in detail above, the electricalconnector has a groundplane that differentially conducts currentresponsive to frequency. A second counterpoise 604 is connected to theelectrical connector second end 610 to supply an antenna ground throughthe electrical connector 100, responsive to antenna radiation frequency.

As explained above, such a design is useful in eliminating the influenceof the second counterpoise 604. When no ground current flows through theconnector 100, the second counterpoise 604 has no effect upon theantenna 612. Alternately, the connector 100 can be used to changeantenna patterns. For example, at a first frequency the antenna can havea first pattern as a result (exclusively) of the first counterpoise 602,if the connector conducts no ground current at the first frequency. At asecond frequency, the antenna 612 can have a different, intended patternas a result of the using both the first and second counterpoises. Thatis, the second pattern is a result of conducting ground current throughthe connector 100. Other patterns can be created as a result ofcontrolling the amount of ground current being conducted through theconnector.

Functional Description

FIG. 8 is a schematic diagram depicting the first groundplane conductivetrace of FIG. 3. The groundplane acts as a type of low pass filter,creating high impedance paths for the input reference voltage at somefrequencies, and low impedances at other frequencies. As can beappreciated by one of skill in the art having the benefit of the presentdisclosure, low pass, high pass, bandpass pass, and other conventionalfilter designs can be realized by appropriately arranging the size,placement, distance between elements, inductance, and signal path of thegroundplane.

FIG. 7 is a flowchart illustrating a method for conducting groundcurrent in an electrical connector, responsive to frequency. Althoughthe method is depicted as a sequence of numbered steps for clarity, thenumbering does not necessarily dictate the order of the steps. It shouldbe understood that some of these steps may be skipped, performed inparallel, or performed without the requirement of maintaining a strictorder of sequence. The method starts at Step 700.

Step 702 provides a flexible conductor comprising a signal medium and agroundplane medium with a transmission line pattern (See FIGS. 2Athrough 2D). Step 704 receives a radiated electromagnetic signal. Step706 induces current through the groundplane medium responsive to thefrequency of the radiated signal. In one aspect, receiving the radiatedsignal in Step 704 includes receiving a signal radiated at a firstfrequency. Then, inducing current through the groundplane medium in Step706 includes minimally inducing current through the groundplane mediumat the first frequency.

In another aspect, Step 702 connects segments of a wirelesscommunications device via the connector, and Step 704 receives a signalradiated from (or received by) one of the device segments. Then, Step708 minimally induces current through the signal medium at the firstfrequency. In a different aspect, Step 704 receives a signal at a secondfrequency. Then, Step 708 induces a first current through thegroundplane medium at the first frequency, while inducing a secondcurrent through the groundplane medium at the second frequency, greaterthan the first current. Note, the first and second currents are notnecessarily induced simultaneously.

A flexible connector with a frequency-tuned groundplane has beenpresented. Examples of particular layers, layer orders, and transmissionline patterns have been provided to illustrate the invention. However,the invention is not limited to merely these examples. Other variationsand embodiments of the invention will occur to those skilled in the arthaving the benefit of the present disclosure.

1. An electrical connector with a frequency-tuned groundplane, theconnector comprising: a signal medium comprising a single layer offlexible dielectric material with a conductive trace and having a firstsignal end to accept an electrical signal and a second signal end tosupply the electrical signal; and a frequency-tuned groundplane mediumadjacent the signal medium having a first groundplane end to accept areference voltage, defined with respect to the electrical signal, thegroundplane medium supplying, responsive to frequency, the referencevoltage through a second groundplane end of the frequency-tuned whereingroundplane medium the frequency tuned groundplane medium comprising: afirst groundplane layer of flexible dielectric material with aconductive trace including a plurality of first conductive patches,overlying the signal layer; and a second groundplane layer of flexibledielectric material with a conductive trace in electrical communicationwith the first groundplane layer conductive trace, the secondgroundplane layer underlying the signal layer.
 2. The connector of claim1 wherein the first groundplane layer conductive trace comprises aconductive trace pattern; and wherein the second groundplane layerconductive trace is connected to the first groundplane layer conductivetrace through a plurality of conductive vias.
 3. The connector of claim2 wherein the first groundplane layer conductive trace further includesa second plurality of patches connected through via connections to thesecond groundplane layer conductive trace.
 4. The connector of claim 3wherein each of the first plurality of patches is capacitively coupledto the second groundplane layer conductive trace through one of thesecond plurality of patches.
 5. The connector of claim 4 wherein each ofthe first groundplane layer second plurality of patches has a width anda length; wherein each of the first groundplane layer first plurality ofpatches has a length and an inductance associated with its width;wherein the first groundplane layer has a first edge and a second edge;wherein the first groundplane layer conductive trace comprises thesecond plurality of patches placed consecutively lengthwise along eachedge of the layer, capacitively coupled by a third spacing; and whereinthe first groundplane layer conductive trace comprises the firstplurality of patches placed consecutively lengthwise, capacitivelycoupling the inductance of each patch with a fourth spacing, andseparated widthwise from the second plurality of patches at each edge,capacitively coupled by a fifth spacing.
 6. The connector of claim 2wherein the first groundplane layer conductive trace pattern includes aplurality of patches, each patch having an inductance associated withits length and a via connection to the second groundplane conductivetrace; and wherein the first groundplane layer conductive tracecomprises the plurality of patches, placed consecutively lengthwise,capacitively coupled by a first spacing.
 7. The connector of claim 6wherein the first spacing has a shape selected from the group comprisinga straight line, a stepped pattern, and a saw-toothed pattern.
 8. Theconnector of claim 2 wherein the first groundplane layer conductivetrace includes a plurality of patches, each patch having a width and avia connection to the second groundplane conductive trace; and whereinthe first groundplane layer conductive trace comprises the plurality ofpatches, placed consecutively widthwise, capacitively coupled by asecond spacing.
 9. The connector of claim 2 wherein the secondgroundplane layer conductive trace comprises a second conductive tracepattern underlying a substantially uniform region of the firstgroundplane layer conductive trace; and wherein the first groundplanelayer conductive trace pattern overlies a substantially uniform regionof the second groundplane layer conductive trace.
 10. The connector ofclaim 2 wherein the second groundplane layer is a substantially uniformconductive trace.
 11. The connector of claim 1 wherein the signal layerflexible dielectric material is a material selected from the groupincluding polyester, polyimide film, synthetic aromatic polyamidepolymer, phenolic, polytetrafluoroethylene (PTFE), chlorosulfonatedpolyethylene, silicon, ethylene propylene diene monomer (EPDM), andpaper; and wherein the signal layer conductive trace is a materialselected from the group including copper, silver, conductive ink, andtin.